1. Field of the Invention
The present invention generally pertains to the field of electronic devices and, in particular, to a method and apparatus for the thermal management of electronic devices.
2. Background Information
It is known that electronic devices dissipate heat during operation. More specifically, the electronic components comprising electronic devices dissipate heat. Thermal management, i.e., the ability to keep temperature sensitive elements within the electronic device within a prescribed operating temperature, has evolved to address the increased temperatures created within such electronic devices as a result of increased processing speed/power of the internal electronic components. Historically, electronic devices were cooled by a natural convection thermal management technique. That is, the cases or packaging of these prior art electronic devices were designed with openings (e.g., slots) strategically located to allow warm air to escape and cooler air to be drawn in.
However, with the advent of high performance processors such as, for example, the Intel Pentium.RTM. Pro processor, have required more innovative thermal management. For example, in the last several years processing speeds of computer systems have climbed from 25 MHz to over 233 MHz. Similarly, smaller hand-held devices such as, for example, personal digital assistants (PDA) have also benefited from improved processor technology with ever increasing processing speeds and power. Each of these increases in processing speed and power generally carry with it a "cost" of increased heat dissipation. Corresponding improvements in thermal management technology accompanied, out of necessity, such technological improvements. Simple convection, no longer sufficient to provide proper thermal management, was either supplanted or assisted by forced air thermal management techniques and the addition of passive heat dissipating devices, e.g., heat sinks, to temperature sensitive devices. For example, some prior art computer systems have resorted to thermally coupling a heat sink to the "heat slug" or "thermal plate" (e.g., top cover) of the processor in an effort to remove the heat from the temperature sensitive core of the processor, wherein a system fan is responsible for remove the heated air from within the system chassis. Indeed, some of these new high speed systems require multiple fans, some of which are dedicated to individual processor(s) with a dedicated heat sink to maintain proper operating temperatures.
Those skilled in the art will appreciate, however, that the additional fans and heat sinks necessary for prior art forced air cooling systems result not only in an added expense for manufacturers of such electronic devices, but they are often bulky and require an inordinate amount of real estate within the electronic device. Fans have notoriously poor reliability problems, and thus will fail after years of prolonged use well before other components of the electronic device. Further, the additional fans increase the acoustic and electrical "noise" of the electronic device, as well as increasing the likelihood of a reliability failure of the electronic device. Another shortcoming of prior art forced air thermal management solutions is that although operating temperatures within an electronic device may fluctuate during operation, many of the forced air cooling systems of the prior art merely have two modes of operation: on and off. Those skilled in the art will appreciate that such use generally results in premature wearing of the fan bearings, resulting in an increase in acoustical noise. With an effort by most in the industry to reduce the size of electronic devices while increasing their reliability, the increased cost and space requirements necessitated by multiple fans is not an attractive thermal management solution.
Thus a need exists for a method and apparatus for the thermal management of electronic devices that is unencumbered with the deficiencies and limitations inherent in the prior art.